1. Technical Field of the Invention
The present invention relates to a programmable controller system including a base board, and a power supply unit and a CPU unit which are to be mounted on the base board.
2. Background of the Related Art
Conventionally, there has been a system, such as a programmable controller, having a configuration in which various units are mounted on a base board (see Unexamined Japanese Patent Publications No. Hei-4-308952, No. Hei-2-116903, No. Hei-1-175607, No. Hei-2-176833, or the like).
FIG. 13 is a diagram showing a system configuration of a conventional programmable controller system constituted by a base board Bxe2x80x3, a power supply unit SUxe2x80x2 for supplying power, a CPU unit CUxe2x80x2 for performing input/output processing and various arithmetical operations, input/output units (I/O units) IU1, . . . , IUn for input/output operations, and so on, those units being mounted on the base board Bxe2x80x3. The power supply unit SUxe2x80x2, the CPU unit CUxe2x80x2, the I/O units IU1, . . . , IUn are attached to slots provided in the base board Bxe2x80x3 respectively, and have mating connectors which are to be connected to connectors provided in the respective slots. The base board Bxe2x80x3 to which the CPU unit CUxe2x80x2 is to be attached is called a fundamental base board. On the other hand, there is also an extension base board connected to an extension connector 13 provided in the base board Bxe2x80x3 through an extension cable, and used for extending the I/O units IU1, . . . , IUn and so on. Basically, only the power supply unit SUxe2x80x2, the I/O units IU1, . . . , IUn and so on, are attached to such an extension base board, but the CPU unit CUxe2x80x2 is not attached thereto. In the figures, the CPU unit CUxe2x80x2 is shown as an unit occupying two slots.
In the fundamental base board Bxe2x80x3, a power supply connector 15 to which the power supply unit SUxe2x80x2 is to be connected, a CPU connector 16 to which the CPU unit CUxe2x80x2 is to be connected, I/O connectors 171, . . . , 17n to which the I/O units IU1, . . . , IUn are to be connected, and the extension connector 13 are connected through a power supply line Lp, while an address bus AB and a data bus DB are provided among the CPU connector 16, the I/O connectors 171, . . . , 17n and the extension connector 13.
In addition, base board selection signals US3 and US4 for selecting the fundamental base board Bxe2x80x3 and the extension base board respectively, and I/O selection signals US0 to US2 for selecting the I/O units IU1, . . . , IUn attached to the slots of the respective base boards are outputted from the CPU unit CUxe2x80x2. These selection signals are supplied through the CPU connector 16 to a select circuit 18 provided on the fundamental base board Bxe2x80x3. In the select circuit 18, slot selection signals are supplied to selected ones of the I/O connectors 171, . . . , 17n connected to the I/O units IU1, . . . ,IUn in accordance with the supplied selection signals. In such a manner, input/output of data is performed through the address bus and the data bus between the I/O units IUI, . . . , IUn supplied with the slot selection signals through the I/O connectors 171, . . . , 17n and the CPU unit CUxe2x80x2.
On the other hand, the respective slots are arranged in a row in the fundamental base board Bxe2x80x3 and the extension base board Bxe2x80x3. Attached to the respective slots 0, . . . , n, the power supply unit SUxe2x80x2, the CPU unit CUxe2x80x2, and the I/O units IU1, . . . , IUn are disposed side by side adjacently as shown in FIG. 14(a).
However, when the power supply unit is a high capacity power supply unit SUxe2x80x3, the body size thereof is so large that the power supply unit occupies two slots (the power supply slot and the slot 0) of the fundamental base board Bxe2x80x3 as shown in FIG. 14(b). In this case, since the slot 0 to which the CPU unit CUxe2x80x2 is to be attached originally is occupied by the power supply unit SUxe2x80x3, the CPU unit CUxe2x80x2 must be shifted so as to be attached to the adjacent slot 1. Then, the slots to which the I/O units IU1, . . . , IUn are to be attached are shifted one by one successively in such a manner that, for example, the slot to which the I/O unit IU1 is to be attached is shifted from the slot 1 to the slot 2. Therefore, there is a problem that the select numbers of the I/O units IU1, . . . , IUn (the numbers for identifying the I/O units IU1, . . . , IUn) change when wiring is made so as to fix the slot selection signals from the select circuit 18 as described above. In addition, when the fundamental base board Bxe2x80x3 and the extension board are compared with each other, the physical positions of the slots and select numbers become different in accordance with presence or absence of the attachment of the CPU unit CUxe2x80x2 as shown in FIGS. 14(a) and (b). It is therefore necessary to provide the fundamental base board Bxe2x80x3 and the extension board separately since the base boards cannot be used with each other commonly.
It is an object of the present invention to solve the foregoing problem, that is, to provide a base board, and a power supply unit and a CPU unit which are attached to the base board, in which slots to which I/O units and so on are attached can be recognized properly even when the width of the power supply unit and the CPU unit are changed independently and respectively, or even when the CPU unit is not attached.
To achieve the above object, according to the present invention, there is provided a programmable controller system comprising: a base board having a plurality of slot; a power supply unit attached to at least one of the slots for supplying power to the base board; a CPU unit attached to at least one of the slots for outputting an I/O unit specification signal for specifying one executing I/O unit from among at least one I/O unit attached to ones of the remaining slots for executing I/O processing; discrimination means for discriminating amount of shifted position of the I/O unit which is changed in accordance with number of slot occupied by the power supply unit and the CPU unit; correction means for correcting the I/O unit specification signal based on the amount of shifted position of the I/O unit discriminated by the discrimination means; selection means for selecting one actual slot in which the I/O unit specified by the I/O unit specification signal is attached based on the corrected I/O specification signal.
Specifically, the discrimination means includes a first circuit having an unchanged configuration, a second circuit having a variable configuration according to the number of slot occupied by the power supply unit, and a third circuit having a variable configuration according to the number of slot occupied by the CPU unit, and wherein the amount of shifted position of the I/O unit is uniquely determined by a combination of the first circuit, the second circuit, and the third circuit.
The first circuit is a logic circuit provided on the base board, the second circuit is provided in the power supply unit, and the third circuit is provided in the CPU unit, and the first circuit, the second circuit and the third circuit uniquely form a discrimination circuit outputting a discrimination signal to the correction means when the power supply unit is attached to the base board.
In the system, it is possible to obtain different identification signals respectively when the widths of the power supply unit and the CPU unit occupying the slots of the base board are changed independently, or when the CPU unit is not attached. Accordingly, even in such a case, it is possible to properly recognize the slots to which I/O units and so on are attached.
Furthermore, according to the present invention, there is also adopted a method for switching a function of a base board in the programmable controller system. The method comprises the steps of: attaching a power supply unit for supplying power to the base board to at least one of a plurality of slots provided on the base board; attaching removably to one of the slot a CPU unit for outputting an I/O unit specification signal for specifying one executing I/O unit from among at least one I/O unit attached to ones of the remaining slots for executing I/O processing; detecting whether the CPU unit is attached to the base board; when presence of attachment of the CPU unit is detected, discriminating amount of shifted position of the I/O unit which is changed in accordance with number of slot occupied by the power supply unit and the CPU unit; correcting the I/O unit specification signal based on the amount of shifted position of the I/O unit discriminated by the discrimination means; selecting one actual slot in which the I/O unit specified by the I/O unit specification signal is attached based on the corrected I/O specification signal; and switching a control signal terminal provided on the base board as an output terminal, and when absence of attachment of the CPU unit is detected, switching the control signal terminal as an input terminal and taking in the I/O unit specification signal from an external unit through the control terminal; discriminating amount of shifted position of the I/O unit which is changed in accordance with number of slot occupied by the power supply unit; correcting the I/O unit specification signal based on the amount of shifted position of the I/O unit discriminated by the discrimination means; and selecting one actual slot in which the I/O unit specified by the I/O unit specification signal is attached based on the corrected I/O specification signal.
In the method, when the absence of the CPU unit is detected, the amount of shifted position of the I/O unit is uniquely determined by combining a first circuit and a second circuit, the first circuit is provided in the base board with a unchanged configuration and the second circuit is provided in the power supply unit with a various configuration according to the number of slot occupied by the power supply unit.
In the method, when the presence of the CPU unit is detected, the amount of shifted position of the I/O unit is uniquely determined by combining a first circuit, a second circuit, and a third circuit, the first circuit is provided in the base board with a unchanged configuration, the second circuit is provided in the power supply unit with a various configuration according to the number of slot occupied by the power supply unit, and the third circuit is provided in the CPU unit with a various configuration according to the number of slot occupied by the CPU unit.
Accordingly, one and the same base board can be used in common both as the fundamental base board and the extension base board in accordance with the presence or absence of attachment of the CPU unit.